1. Field of the Invention
The present invention relates to compost excellent in fertilizing activity, and to its production. The present invention can be applied for treating particularly agricultural waste, for example, organic waste rich in vegetable scrap or the like dumped from fruit and vegetable markets and for producing therefrom compost excellent in fertilizing activity.
2. Description of the Related Art
Organic waste such as urban rubbish (such as kitchen waste), sewage sludge, excreta from stock raising, and trash from agricultural production can be converted under appropriate conditions (for example in the presence of microorganisms) into compost which is then recycled to soil for reuse as fertilizer.
As for some organic wastes treated in compost treating equipment, although there are cases where organic wastes are masses consisting of various organic substances such as urban rubbish, there are not a few cases where composition of the wastes is comparatively homogeneous such as sewage sludge, excreta from stock raising, trash from fruit and vegetable markets, or waste from fish markets. For such waste composed of organic substances comparatively homogenous in composition to be treated to produce compost, certain appropriate conditions exist or likely exist which can be chosen according to the composition of those organic substances or the property of a resulting mass.
For example, it is a feature that agricultural waste, particularly garbage damped from fruit and vegetable markets contains a rich amount of vegetable scrap, and hence it has a high carbon/nitrogen ratio (C/N ratio) and fiber content as compared with kitchen waste, sewage sludge, and excreta from stock raising, though of course not as high as those of sawdust or timber tips.
Generally, many studies have been reported heretofore as regards the methods how to treat organic wastes to produce compost. Some items such as water content, porosity, pH, and C/N ratio of a material to be turned into compost are proposed to be considered in the compost treatment. The carbon/nitrogen ratio of a compost material has been known as a factor which may greatly affect the rate at which the material is converted into a finished compost, and it is generally said that, with a material having a carbon/nitrogen ratio of 7-30, decomposition of organic substances takes place rapidly, and with a material having a carbon/nitrogen ratio of 7-10, organic substances decompose most rapidly. Also it has been known that the carbon/nitrogen ratio is 30-50 for common urban rubbish, 8-12 for sewage sludge, and about 10-20 for product compost which has received a compost treatment.
Further, according to the description of Japanese Unexamined Patent Publication No. 57-11895, it is described that sufficiently ripe compost can be produced in a short time when a compost material which meets the conditions such as a carbon/nitrogen ratio of 12-25 and a water content of 60-85% is treated under a certain air supply condition. Furthermore, in Japanese Unexamined Patent Publication No. 61-97181, is described a method that organic compost fermented and dried in a short period can be obtained by controlling air evacuation from a sealed type fermentation tank to which warm air is ventilated, and it is also described that a compost material should preferably have a carbon/nitrogen ratio of 10-20 and a water content of 50-70%.
As described above, of compost materials and particularly compost having received a compost treatment, with a carbon/nitrogen ratio of 10 or less, discussion has been seldom made with an emphasis on their quality.
According to what the present inventors have found, even if garbage dumped from fruit and vegetable markets, to be made into compost, is initially so adjusted as to have a carbon/nitrogen ratio of 12-25 during a preparation stage, then receives an appropriate compost treatment, and thus obtained compost has a carbon/nitrogen ratio of 10-20, the resulting compost, when applied to soil to see its fertilizing effect, will not give a result as expected. Briefly, they found that this method can not provide compost excellent in fertilizing activity.